CN215450920U

CN215450920U - Passive device for relieving broken siphon after LOCA accident

Info

Publication number: CN215450920U
Application number: CN202121576773.6U
Authority: CN
Inventors: 吴燕华; 戚展飞; 杨子江; 胡楠; 曹臻
Original assignee: Shanghai Nuclear Engineering Research and Design Institute Co Ltd
Current assignee: Shanghai Nuclear Engineering Research and Design Institute Co Ltd
Priority date: 2021-07-12
Filing date: 2021-07-12
Publication date: 2022-01-07
Anticipated expiration: 2031-07-12

Abstract

The utility model aims to disclose a passive device for relieving broken siphon after LOCA accident, which comprises a helical blade, an impeller shaft, a rotary impeller, a blowing pipe and a pipe sleeve, wherein the helical blade is arranged on the impeller shaft; the helical blade is fixedly arranged on the impeller shaft, the lower ends of the impeller and the impeller shaft are fixedly connected with the inner wall of the pipe sleeve in a welding manner, and the impeller and the helical blade are connected in a matching manner; the blowing pipe is arranged below the pipe sleeve, the reference line of the blowing pipe is aligned with the reference line of the sleeve, and the blowing pipe and the sleeve are fixedly assembled through a bracket or a hoisting device respectively; compared with the prior art, the pipeline directly connected with the reactor coolant system needs to be deeply inserted into the pressure vessel, when the pipeline outside the pressure vessel is broken, because the rotational flow resistance generated by the rotary impeller and the helical blade is large, the leakage amount of the reactor coolant passing through the device and the break is reduced, the accident consequence is relieved, on the other hand, the development speed of the accident is also delayed, so that the operator has enough time to process the accident, and the purpose of the utility model is realized.

Description

Passive device for relieving broken siphon after LOCA accident

Technical Field

The utility model relates to a passive device, in particular to a passive device which is suitable for relieving broken siphon after LOCA accident in a nuclear power plant.

Background

Depending on the process requirements, some of the pipes need to be deep inside the reactor pressure vessel, and when the part of the pipe outside the reactor pressure vessel is broken, the pipe from the break opening to the inside of the pressure vessel becomes a siphon, and the siphon is caused under the driving of the pressure difference between the break opening position and the coolant liquid level in the pressure vessel (i.e. the siphon suction force), i.e. the coolant with high temperature, high pressure and high radioactivity in the pressure vessel is sprayed out from the break opening through the siphon due to the siphon force and the pressure in the reactor, and the loss of coolant accident (LOCA accident) is formed.

The consequences of this accident are more severe than the LOCA accident, which does not require the consideration of siphonage. Because the pipeline goes deep into the pressure vessel, the siphoning phenomenon can be stopped only when the level of the coolant leaked into the containment vessel and the level of the liquid in the pressure vessel are kept flat. The accident causes: 1) the coolant in the pressure vessel leaks in a large quantity, the cooling capacity of the reactor core is greatly reduced, the reactor core is greatly exposed, the heat transfer capacity is greatly reduced, fuel elements are damaged, and the reactor core is molten; 2) high-temperature and high-pressure coolant is sprayed into the containment vessel to threaten the integrity of the containment vessel; 3) after radioactive substances in the coolant enter the containment vessel, if the containment vessel leaks, the environment is polluted.

Currently, systems lack effective human intervention to mitigate the LOCA accident caused by siphoning. The siphon phenomenon at the break not only poses a threat to the safety of the reactor itself, but also can seriously pollute the surrounding environment.

Therefore, there is a particular need for a passive device that alleviates break siphoning following a LOCA accident to address the above-mentioned existing problems, and which is capable of delivering coolant deep into the pressure vessel along a pipeline during normal operation, and which meets coolant delivery flow requirements, i.e., does not affect normal delivery of coolant.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a passive device for relieving broken siphon after LOCA accident, aiming at the defects of the prior art, the broken siphon after the LOCA accident can be effectively relieved in a short time, and the safety of a nuclear power plant is improved.

The technical problem solved by the utility model can be realized by adopting the following technical scheme:

a passive device for relieving broken siphon after LOCA accident is characterized by comprising a helical blade, an impeller shaft, a rotary impeller, a blowing pipe and a pipe sleeve; the helical blade is fixedly arranged on the impeller shaft, the lower ends of the impeller and the impeller shaft are fixedly connected with the inner wall of the pipe sleeve in a welding manner, and the impeller and the helical blade are connected in a matching manner; the blowing pipe is arranged below the pipe sleeve, the reference line of the blowing pipe is aligned with the reference line of the sleeve, and the blowing pipe and the sleeve are fixedly assembled through a support or a hoisting device respectively.

In one embodiment of the utility model, the spiral blade is a solid spiral type, and has the advantages of strong rigidity, high strength, difficult fracture and stable and reliable operation.

In one embodiment of the utility model, the impeller is a cyclonic inducing impeller.

In one embodiment of the utility model, the passive device is arranged in the pressure vessel and is connected with a pipeline needing to be deeply arranged in the pressure vessel, and the passive device is arranged at the top in the pressure vessel.

In one embodiment of the utility model, the passive device is vertically connected with the pipeline, one end of the passive device is directly connected with the pipeline deep into the pressure vessel, and the other end of the passive device is directly connected with the pipeline outside the pressure vessel.

The passive device for relieving broken siphon after LOCA accident comprises the following working processes:

when the device normally operates, coolant flows downwards into the reactor pressure vessel from the outside of the reactor pressure vessel through a pipeline connected with the passive device for relieving broken siphon after LOCA accident, the coolant mainly flows downwards through an unobstructed annular area around the helical blade, the pressure drop is small, and the requirement of coolant conveying flow speed can be met. And the coolant can be sent to the deep part of the pressure vessel along the pipeline without leaking to the top of the reactor pressure vessel from the pipe sleeve, and the requirement of coolant delivery flow can be met.

When the pipeline outside the pressure container is broken, the pipeline from the broken opening to the pressure container is changed into a siphon, and the coolant of a coolant system in the pressure container reversely enters the passive device for relieving broken opening siphon after LOCA accident through the pipeline or enters the passive device for relieving broken opening siphon after LOCA accident through a spraying pipe due to siphon suction and pressure difference inside and outside the reactor. The coolant forms rotational flow motion through the rotary impeller at the lower part, and then the fluid continuously flows in a rotational flow mode through the helical blades, so that higher pressure drop is generated, the coolant quantity of the passive device for relieving the broken siphon after the LOCA accident is reduced, and the leakage quantity of the coolant at the broken opening is reduced; when the coolant liquid level in the pressure container drops below the spraying pipe, the gas in the pressure container can enter the passive device for relieving the broken siphon after the LOCA accident through the spraying pipe, so that the coolant amount entering the passive device for relieving the broken siphon after the LOCA accident and the broken siphon after the LOCA accident is reduced, and the effect of relieving the broken siphon after the LOCA accident is achieved.

Compared with the prior art, the passive device for relieving the broken siphon after the LOCA accident has the advantages that the passive device is directly connected with a reactor coolant system and needs to go deep into a pipeline in a pressure container, when the pipeline outside the pressure container is broken, because the rotational flow resistance generated by the rotary impeller and the helical blades is large, the leakage amount of the reactor coolant passing through the device and the broken opening is reduced, the accident result is relieved, on the other hand, the development speed of the accident is delayed, so that an operator has enough time to process the device, and the purpose of the passive device is realized.

The features of the present invention will be apparent from the accompanying drawings and from the detailed description of the preferred embodiments which follows.

Drawings

FIG. 1 is a schematic structural view of a passive device for relieving break siphoning after a LOCA accident according to the present invention;

fig. 2 is a schematic cross-sectional view taken along line a-a in fig. 1.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the utility model easy to understand, the utility model is further explained below by combining the specific drawings.

Examples

As shown in fig. 1 and 2, the passive device for relieving broken siphon after LOCA accident of the utility model comprises a helical blade 1, an impeller shaft 2, a rotary impeller 3, a sleeve 4 and a blowing and discharging pipe 5. The helical blade 1 is fixed on the impeller shaft 2, the lower ends of the impeller 3 and the impeller shaft 2 are fixedly connected with the inner wall of the pipe sleeve 4 in a welding mode, and the impeller 3 is connected with the helical blade 1 in a matching mode so that fluid can continuously flow in a swirling mode in the device.

The helical blades 1 are solid helical, the rigidity is strong, the strength is high, the fracture is not easy, the operation is stable and reliable, each helical blade 1 can rotate left or right, the pitch range is 0.5-5 times of the inner diameter of the sleeve 4, the thickness of the helical blade 1 is 1-20mm, and the outer diameter of the helical blade 1 is 0.1-0.9 times of the inner diameter of the sleeve 4.

The length of the impeller shaft 2 is 5-10 times of the inner diameter of the sleeve 4, and the outer diameter of the impeller shaft 2 is 0.1-0.5 times of the inner diameter of the sleeve 4.

The rotary impeller 3 is a rotational flow type induction impeller, the number of blades is more than or equal to 3, the included angle between each blade and the impeller shaft 2 can be 0-45 degrees, and each blade can be a straight blade or has a certain radian.

The blow-off pipe 5 is arranged below the pipe sleeve 4, the reference line of the blow-off pipe 5 is aligned with the reference line of the pipe sleeve 4, the blow-off pipe 5 and the pipe sleeve 4 are fixedly assembled through a support or a hoisting device respectively, the maximum inner diameter of the blow-off pipe 5 can be 1.5-3 times of the inner diameter of the pipe sleeve 4, and the minimum pipe diameter can be the pipe diameter of a pipeline connected with the blow-off pipe or the pipe diameters of other sizes.

The passive device for relieving the broken siphon after the LOCA accident is made of metal (such as stainless steel, carbon steel or aluminum alloy) or high polymer material (such as polyimide or polytetrafluoroethylene), and can resist the high-temperature and high-irradiation conditions after the accident.

When the device normally operates, the coolant flows downwards into the reactor pressure vessel from the outside of the reactor pressure vessel through the pipeline where the device is located, the coolant mainly flows downwards through the unobstructed annular area around the helical blade 1, the pressure drop is small, and the requirement of coolant conveying flow speed can be met. And the coolant can be sent to the deep part of the pressure vessel along the pipeline without leaking to the top of the reactor pressure vessel from the pipe sleeve, and the requirement of coolant delivery flow can be met.

When a breach occurs in a pipe outside the pressure vessel, the pipe from the breach into the pressure vessel becomes a siphon through which coolant from the coolant system in the pressure vessel will enter the device due to siphon forces and in-pile pressure, or through the blow-off pipe 5 of the device. The coolant enters the rotary impeller 3 at the lower part of the device to start rotational flow movement, and then the fluid is forced to continue rotational flow through the helical blades 1, so that higher pressure drop is generated, the coolant amount passing through the device is reduced, the leakage amount of the coolant at the break is reduced, and the effect of relieving the break siphon after the LOCA accident is achieved. When the coolant liquid level in the pressure container is reduced to be below the inlet of the spraying pipe 5, the gas in the pressure container enters the passive device for relieving the broken mouth siphon after the LOCA accident through the spraying pipe 5, so that the leakage amount of the coolant of the broken mouth is reduced, the effect of relieving the broken mouth siphon after the LOCA accident is achieved, and the safety allowance after the accident is improved.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the utility model, which is defined by the appended claims and their equivalents.

Claims

1. A passive device for relieving broken siphon after LOCA accident is characterized by comprising a helical blade, an impeller shaft, a rotary impeller, a blowing pipe and a pipe sleeve; the helical blade is fixedly arranged on the impeller shaft, the lower ends of the impeller and the impeller shaft are fixedly connected with the inner wall of the pipe sleeve in a welding manner, and the impeller and the helical blade are connected in a matching manner; the blowing pipe is arranged below the pipe sleeve, the reference line of the blowing pipe is aligned with the reference line of the sleeve, and the blowing pipe and the sleeve are fixedly assembled through a support or a hoisting device respectively.

2. The passive means of mitigating post-LOCA accident break-up siphon of claim 1, wherein said helical blade is of a solid helical type.

3. The passive means of mitigating a breaching siphon after a LOCA accident of claim 1, wherein said rotary impeller is a swirl inducing impeller.

4. The passive device for relieving post-LOCA accident break siphon of claim 1, wherein said passive device is installed in the pressure vessel and connected to the pipeline to be extended into the pressure vessel, said passive device is installed on the top of the pressure vessel.

5. The passive device for relieving post-LOCA accident break siphon of claim 1, wherein said passive device is vertically connected to a pipeline, one end of said passive device is directly connected to a pipeline extending deep into the pressure vessel, and the other end of said passive device is directly connected to a pipeline outside the pressure vessel.